#include<stdio.h>
unsigned long Fibonacci( int n );
int main(void)
{
    int n;
    scanf("%d",&n);
    printf("%ld", Fibonacci(n));
    return 0;
}

unsigned long Fibonacci( int n )
{
    if (n > 2)
       return Fibonacci(n - 1) + Fibonacci(n - 2);
    else
       return 1;
}